The method "Int32 ToInt32 (System. String)

If (! String. isNullOrEmpty (Year) {// The first method var y = Convert. toInt32 (Year); pInfo = pInfo. where (p => p. startTenderDate_T.Value.Year = y); // The second method is pInfo = pInfo. where (p => p. startTenderDate_T.Value.Year = Convert. toInt32 (Year ));} both methods aim to filter data with the date of Year, but the first method can recognize the data. The second method cannot be identified. (The method "Int32 ToInt32 (system. string) error. The reason is that the convert method cannot be recognized in the second linq expression. because the where clause cannot call C # methods such as convert, or add the int type to tostring or put it in the where clause, because it needs to parse the lamda expression rather than parse C # to understand this, you must have a deep understanding of lambda expression parsing.